Rotative wing aircraft



Jan. 12, 1937. R HA I ROTATIVE WING AIRCRAFT Filed July 27, 1935 @aou] K9" er I N VI: NToE.

Patented Jan. 1.2, 1937 UNITED STATES PATENT OFFICE In Great B 4 Claims.(CI. 24449) This inventim relates to rotative wing aircraft,

. that is to say aircraft comprising a system of supporting surfaces orblades rotative about a vertical or approximately vertical axis, usuallytermed windmill planes and helicopters.

It is an improvement in or modification of that set forth in Britishpatent, application No. 23,645/33 according to which each blade of ahelicopter or windmill plane is connected, at a point intermediate itsends, to the hub by a tor-' sionally flexible radial tension member toeliminate friction in adjusting the angle of the blade.

In' such machines, particularly of the type known as windmill machines,the tension member provides a considerable stabilizing torque 1: it canbe-flxed at some neutral position (such as the auto-rotating angle) andtherefore tends to return to this position when the blade has beenturned to some other angle by means of the control directing theaircraft. It is, however, essential that the means for fixing the saidblade shall be capable of taking a considerable torsional load withoutslipping and that the said fixing means shall occupy only a small spaceto be capable of being accommodated within a tubular spar carrying theblade.

According to the invention each blade is connected, at a pointintermediate its ends, to the hubby a torsionally flexible radialtension memher, means being provided for fixing the ends of v the saidtension member in any adjusted position so that the torsional load onthe said tension member acts as a'restorlng couple to the said blade.

The ends of the torsionally flexible member may be provided with malethreads which engage corresponding female threads in the hub or bladeand either the said threaded ends or the correspondingmortions of thehub or blade may be .split so-that, by means of axially tapered devices,the male and female threads may be forced into engagement, therebylocking the torsionally flexible member in adjusted position.

Anexample of construction-according to the invention applied to aircraftof the kind set forth in British patent, application No. 31,300/33 isdescribed with reference to the accompanying drawing whereim- Figure 1shows a vertical cross section of the root of a blade and inner end ofthe torsionally I flexible member.

- Figure 2 shows a corresponding cross sectional view of the outer endof the torsionally flexible as member. 7

- rotary hub, a plurality of The torsionally flexible member I isprovided with screw-threaded ends I 2, 3. The outer threaded end 3 isscrewed into a corresponding screw-threaded portion 4 of the blade 5which is split longitudinally by saw cuts 6 and is provided 5 on itsouter surface with a male thread 1 on which is threaded a lock nut 8.Either the lock nut I or the screwed portion I or both may be tapered sothat the splitportlon 4 may be wedged together on to the threaded end 3by tightening 0 up the lock nut I.

The inner threaded end 2 of the member I is split with a longitudinalsaw cut 9 and drilled with an axial hole III which may be eitherparallel or tapered and into which a suitable taper pin Il may bedriven. This pin H may be swivelled in a plug screw II which is adaptedto screw into a threaded hole It in the blade knuckle It. The

end 2 of the torsionally flexible member is threaded into the hole ll.20

when it is in adjusted position the plug screw I2 is tightened upforcing the plug .li into the hole It and thereby w dsing the split ends2 of the torsionally flexible member against the sides of the hole I3.35

In a modification the hole Ill may be threaded andthe taper pin Ii maybe provided with a corresponding thread by which it is screwed intoplace. It will be understood that the hiventioh is 30 applicable to alltypes of.rotating wing aircraft although it is particularly applicableto such machines having blades of the kind described in British patent,application No. 31,300/33.

What I claim and desire to secure by Letters 35 Patent of the UnitedStatesisz- 1. A rotative wing for aircraft, including, a rotary hub, aplurality of variable-pitch sustaining blades radiating therefrom,torsionally resilient tie means anchoring each blade to said hub 40 andtorsionally stressed by pitch changes thereof, and means for ansularlyadjusting either end of said tie means to adjust the pitch angle atwhich its resilience tends to maintain said blade.

2. A rotative wing for aircraft, including a 45 rotary hub, a pluralityof variable-pitch sustaining blades radiating therefrom, torsionallyresilient radial tie means anchoring each blade. at a I pointintermediate in its length, to said hub and torsionally stressed bypitch changes thereof, and

means for angularly adjusting either end of said tie means to adjustthepitch angle at which its resilience tends to maintain said blade.

3. a rotative wins for craft. includin a ble pitch hollow 56 -$e,in1ngblades radiating therein), & tumm e313; resilient ram tie member,extending m a a m eeeh blade to enchm' it, at a point mtex'medlete inits length, to said huh and fwrsionelly swarms}! by pitch changesthereof, and. meme fer e- Emzly adjusting either end of said tie memberm edfiust the pitch angle at which its resiliemee tends t0 maintain saidblade.

e eew eee *3. A rotary g for aircraft as claimed in em 3 wherein an endof said tie member is provided with a male screwthread engaging in afemale sprewthread carried by said blade or hub, @ne ef saidscrewthreads being axially split for emepemtion with an axially movableand tapered m? member.

